Most of the 114 missing Home Office documents potentially linked to child sex abuse allegations in Westminster appear to be routine inquiries from politicians, according to the department's top official.
Permanent Secretary Mark Sedwill said the titles of the files could not be released yet despite a request from the Home Affairs Select Committee, because they contained personal data that needed to be edited out.
But the mandarin said he had reviewed the list, adding: "Most appear to have contained correspondence from Members of Parliament either asking about government policy or on behalf of constituents."
Mr Sedwill said that kind of correspondence would "normally have been destroyed after two years under the file destruction policy of the time".
The official admitted earlier this week that he was "concerned" about the absence of the potentially relevant material, which was identified as missing or destroyed by a review in the Home Office's handling of paedophilia allegations last year.
In a letter to the committee chairman Keith Vaz today, Mr Sedwill said he had done its bidding by studying the list of titles - but could not yet publish it.
"As many of the file titles in the list contain the names of individuals it will have to be redacted before I can provide it to the committee in order both to protect the privacy of the individuals and to avoid the risk of prejudicing ongoing criminal investigations into historic child abuse," he said.
He added that the same applied to the full report of the review - executive summaries of which have already been released.
As a result, they may not be published until a second review of the Home Office's handling of allegations, being carried out by NSPCC head Sir Peter Wanless and Richard Whittam QC is complete in eight to 10 weeks' time.
Mr Vaz insisted it was "implausible" that a redacted list of titles could not be provided more quickly.
"I am disappointed that the names of the lost files have not been provided to the Committee immediately, particularly considering that Mr Sedwill did not feel it necessary to view the details of the files a year ago when this first came to his attention. He has only done so since being asked to last Tuesday," he said.
"Though we welcome the work done by Mr Sedwill in commissioning the original review, it seems implausible that a redacted list of the files cannot be disclosed more quickly.
"It is also deeply worrying that the Home Office does not know of how many people were disciplined for the mistreatment of files at the time of the allegations. I am baffled by lack of monitoring performed by the Home Office relating to those dismissed for this type of breach.
"We will be questioning Theresa May on these issues when she gives evidence to the Committee on Monday."
Mr Vaz said the committee would also be calling Sir Peter and Mr Whittam to give evidence, as well as Baroness Butler-Sloss, who is leading a broader inquiry for the government into whether child abuse allegations were covered up at institutions.
Earlier, Deputy Prime Minister Nick Clegg insisted Lady Butler-Sloss was the right person to lead the inquiry into "revolting" allegations that child abuse was covered up by establishment figures.
The former High Court judge has faced calls to step down after reports that her brother Sir Michael Havers tried to prevent ex-MP Geoffrey Dickens airing claims about a diplomat in Parliament in the 1980s.
But on his LBC phone-in show, Mr Clegg said complaints about the appointment were "really unfair on her", adding: "I think that the idea that because she had a brother in politics at that stage disqualifies her from doing this work, I don't accept that and I think it's right that she has said she is going to carry on doing the job."
Asked by a caller whether he believed there had been a cover-up of abuse, the Liberal Democrat leader said: "I genuinely don't know."
He said there were allegations that powerful men were "not only organising amongst themselves to abuse children but even more revoltingly, then seeking to cover up for each other".